Running In
When I received the review unit, another reviewer had already used it, meaning it was likely already run-in. Nevertheless, since it arrived in an ice-cold state, I left it for two days to unfreeze before switching it on. Then, I let it acclimatize for several more days before listening for the first time. After that, I let it run for over a week before listening again. When I listened to it again, I did not note any sonic differences, which indicated that the MU2 was now at a stable point of operation.
I listened to the MU2 on Artesania and HRS racks, and while there are differences in certain areas, it performs very well on both.
Review Context
The MU2 will be listened to in the context of the main system, which consists of the CH Precision L1 preamplifier, CH Precision A1.5 power amp, and Magico S1 MkII speakers. Other digital sources include the Grimm MU1 and Antipodes Oladra Music Servers, the Aqua LinQ streaming endpoint, and the Aqua La Diva M2 CD transport. Available DACs for comparison include the CH Precision C1.2 and Aqua Formula xHD.
I listened to the MU2 on an HRS EXR audio stand, with a range of footers, and on an Artesania Aire floor platform with Carbon Fiber Linear Arms and KSH2 Krion shelves.
Listening
I started listening to the MU2 as an integrated player using local music and Qobuz streaming, and throughout my listening sessions, the main aspect of the MU2’s performance that stands out the most is that it is a thoroughly refined and well-polished machine. It’s got superb resolution but is never braggy about it. It is fabulously linear, neutral, and precise but, at the same time, always pleasant.
More so than the MU1 (using the average result of a range of DACs used), the MU2 is the antithesis of analytical, let alone clinical. No matter what you play, there is never any harshness, edginess, or even remotely stereotypical digital about it. Still, while it sounds very far from cool, I also can’t say the MU2 is warm per se, and it is most definitely not fat. It’s got fluidity, grace, and charm, and its pacing is spot on, always toe-tapping and neither hurried nor slow.
In many ways, the MU2’s DAC section seems to “simply” pick up and continue in the same vein as its server/streamer part after handing over the signal. Like the MU1, the MU2 sounds neutral yet natural, fast and articulate yet fluid, and accurate without sounding tonally lean.
Having heard the MU1 with a wide range of DACs, I will admit I had a preconception of how the MU2 might sound. It’s a bit like envisioning how a person might look based solely on conversations over the phone – not rooted in reality whatsoever! For some reason, I expected the MU2 to be like a MU1 with a Mola Mola Tambaqui DAC in a single enclosure. For better or for worse, it is not. The MU2’s DAC section does not sound like the Tambaqui (which is brighter and more expressive), nor does it sound like the CH C1.2 (more forceful and robust) or the Aqua Formula xHD (more direct and explicit). In fact, I can’t think of any DAC that the MU2 does sound like. Which kind of makes sense, given their unique DAC topology.
But I realize that still does not really describe what the MU2 does sound like. Let’s break it down into smaller segments to describe the MU2’s performance more accurately.
Starting with the low frequencies, I was pleasantly struck by the precision, articulation, and agility of the MU2’s bass performance. It’s never boomy or bombastic; quite the opposite. Some might find the MU2’s bass to be just a tiny bit lean compared to more voluptuous-sounding servers such as those by Antipodes or Taiko Audio, but flat-out describing the MU2 as lean would be a disservice. Nimble and lightfooted is how I would characterize it.
Moving over all the way to the other end of the spectrum, we find treble that is, quite simply, impossible to fault. It’s highly resolving, explicit, delicate, airy, delightfully fluid, and in no way stereotypical “digital”.
In between these extremes is where something special happens. With tight and articulate bass, one might expect the midrange to be lean or desaturated. This is where the MU2 surprises with density, plushness, and bloom, combined with a laidback gentlemanlike behavior. It’s decidedly calm and quite the opposite of upfront, let alone shouty. This makes for a sound unmistakably highly resolving and transparent yet easy on the ears. It’s weird but the MU2 sounds warm without being warm, if that makes any sense. In any event, I found that the MU2 invites long listening sessions and goes about its way almost anonymously, leaving the music to do its thing.
On balance, you could say that the MU2 is positioned between the Grimm MU1 and the Antipodes Oladra. Assuming a neutral DAC is connected, the three servers are more or less equally capable in terms of resolution and precision, but the MU1 presents the music with a slightly leaner tonal balance and slightly more expressive midrange, whereas the Oladra presents the music with a lusher, more euphonic, and more deeply saturated overall balance. Finally, the servers can also be distinguished by their soundstaging. Whereas the MU2 has superb focus, it comes across as a little more compact than the MU1 with either the CH C1.2 or Aqua Formula xHD DAC, while the Oladra (using AES/EBU) projects the widest and deepest soundstage of the three with the same two DACs. That said, the MU2 has absolutely no trouble imaging outside the speakers, but what happens between them tends to be focused, intimate, and precise rather than breathy or expansive.
Of course, these comparisons are highly dependent on the influence of the external DAC and should thus be taken with a good dose of salt, but still, I hope they are useful in describing the MU2’s sound.
MU2 as a DAC
Besides functioning as an all-in-one server and player, the MU2 also accepts external sources, both analog and digital. Importantly, the analog inputs follow a 100% analog path, so they are not digitized. First and foremost, I wanted to test its AES/EBU input. For this, I used an Aqua La Diva M2 CD transport. But before that, I thought it would be interesting to see what would happen if I connected the MU1 to it. Naturally, that is not a normal use case, but it will allow me more insight into how the MU2’s server and DAC sections behave independently.
So, first up for audition was the MU1, feeding the MU2’s AES/EBU input via a Jorma Audio cable. Switching between the MU2’s internal Roon Core and the AES/EBU input can be done via the menu and dial on top, but is made even easier via the web interface that can be accessed via any device that can run a web browser. The server switches instantly and silently and pauses Roon playback when you switch away from it. Playing the same music from the same source and swapping between the two sources initially felt very similar. But upon listening closer, I detected valid differences… in favor of the MU2!
I found the MU1 to be a little more expressive when combined with a range of DACs than the MU2 by itself, but with the MU1 connected through the MU2, it actually worked out the other way around. Now, the MU2 sounded more expansive, more gushing, and more expressive. Otherwise, the level of detail, the transparency, and the overall character were the same. This tells me that the server part of the two MUs is equally capable, but the integral implementation and direct internal connection place the MU2 at an advantage.
Switching to the Aqua La Diva M2 CD Transport as an AES/EBU source and playing the very CD from which the test file was made, the roles are again reversed. This time, the CD transport sounded a little crisper and livelier and, as a result, just a little more engaging. That’s not really a surprise, though, as this transport had impressed me for the same reasons when I reviewed it earlier and compared it to the MU1. The noted difference is partly due to the CD transport’s spritely nature but also partly attributable to the impact of software updates on how Roon sounds. While we would expect updates only to add features or fix certain aspects of the software, the reality is that they often also affect the sound. To my ears, the impact is more than subtle, but the effects are not devastating. At worst, they make the software sound round and friendly. If you never noticed any changes or never paid attention to this, it’s probably safe to assume the impact is not large enough to worry about.
As my final test to assess the MU2’s performance as a DAC, I used the MU1’s double AES/EBU outputs and two Jorma cables and connected them simultaneously to the MU2 and the Aqua Formula xHD DAC. Then, I fed the same Driade Flow Link Reference 808 cables from both devices to the L1 preamplifier. This allowed me to instantly swap between the two sources using my preamp’s remote control.
I set the MU2 to +4dB on its display to match the gain between the two. Note that the scale in the Roon app shows values different from the Grimm itself. For instance, the unity setting of 0dB on the Grimm equals 92 in Roon, while 100 in Roon equals an actual setting of +8dB on the Grimm, which may overload a preamp input.
Incidentally, I used the same setting when directly comparing the sound of the CH C1.2 DAC to that of the MU2. When testing this in both cases, I was happy to find that the volume control operates very transparently. There is no hardening of the treble, no added edge, and no loss of resolution. Just a higher volume and nothing else, just as one would reasonably expect, but which is not always accomplished.
While switching between the Formula xHD and the MU2 as DACs, I heard notable character differences, confirming my earlier feeling that the MU2 was quite calm and gentlemanlike. While the two DACs have comparable transparency and resolution, the Aqua is upfront, explicit, and exciting, while the MU2 is calm, soothing, composed, and comparatively laidback. It’s a divisive matter but also entirely one of personal taste. I personally like music to be expressive with a high jump factor, but I also know this kind of delivery can be experienced as less romantic, hard, or tiring. Ultimately, I can imagine listeners choosing either presentation with equal validity.
What remains is the matter of value. While 18K euro is a small fortune, many servers cost more while not containing a DAC, or a preamp, for that matter. In that light, it can be considered relatively cost-effective. And one should not overlook the convenience of having the entire front end in a small and attractive package.
Speaking of the MU2’s built-in preamp, let’s see how it performs, shall we?
Next: MU2 direct to a Power Amp, Footers, Cables, and Conclusion
Thank you very much for this review. You continue to be, IMHO, the best audio server reviewer, able to understand and communicate the nuances of these machines, which much more difficult than it seems.
The comments of interconnects and power cables were interesting thanks.
Did the MU2 earn your recomendation?
Great review Christiaan, Question for you. Have you looked at the HiFirRose products? Specifically the 150B and the 130. I am considering the 150B. Matching it with a Bryston 4bsst, Mark Levinson 280S, balanced Cardas cables through out and a Arcam FMJ old school CD player with the Dcs ring dac vintage 2003. Love the sound looking g to progress. My sound is to my ears still excellent..obviously looking to improve however, the all in one unit goes against my audiophile instinct..Your thoughts are very much appreciated
I know of HifiRose but have yet to hear one in my system.
Thanks for the review. I have the Grimm MU1/LS1be/SB1 system. Unsurprisingly, many of your observations correspond to what I hear. It’s the first time since my KLH stereo from college days that the whole system is from 1 manufacturer. And it is quite an accomplishment.
I did read your review actually a few times,.
I have MU2 on order,.
Was surprised Not to see your endorsement for this product.
At Axpona I had dealer switching between Mola Mola T and MU2 . ( he had both connected to rh preamp ) , I could hear a slight difference between the DACs , MMT did sound like it had more authority and was but brighter .
Hope I like the sound of MU2 in my system ( Martin Logan 15a powered by Luxman M900 and MU2 ( hopefully soon )
Hi David,
Between the MU1 with Tambaqui DAC and the integrated MU2, it is a matter of convenience, value, and personal preference. The MU1 allows the user all the freedom to choose a DAC that works synergystically with the system or caters to particular listening preferences. The M2 ticks many boxes and is very cost effective considering it has not only a server and DAC, but also a preamp on board.
As balanced and objective as I try to be with my reviews, they still reflect my personal taste and that, together with the cost/performance ratio and various other factors, defines a component getting a reward or not. What I found was that the MU2’s sonic presentation deviates from the course set by the MU1, meaning that if one loves the MU1 with a given DAC, the MU2 may steer things in another direction. It is a different product, not an automatic guaranteed upgrade. As such, I personally prefer the MU1 and its digital output that allows freedom of DAC selection, and this is reflected in the review.
With all that said, I stand by what I wrote in the review and in the end, a home audition will provide definitive answers. Do let me know the results of your listening session!
Thank you , out of all MU2 reviews I found your most in depth and informative.
I’m patiently waiting for my unit to come.
Might be taken seriously when it supports Spotify Connect. Otherwise it’s misreading its already-niche “audiophile” audience. Aurender, Auralic, Lumin all support Spotify Connect.
Agreed: having more options for streaming services is always better. It’s nice to be able to choose. I use Qobuz and am very pleased with the sound quality but Spotify uses a lossy format at 320kbs, not an audiophile source, and therefore, I don’t feel it is a serious omission.
Spotify is NOT a lossy format as it’s 320kbps vorbis, not mp3 as is often misleading mistaken. Even audiophile ears would struggle to hear the diff between FLAC and Vorbis at 320kbps.
As far as I know, Vorbis is a lossy format. In any case, I’ve not yet heard Spotify sound as good as Qobuz or Tidal.
All digital formats are essentially lossy and the difference is made from LAN connection, power supply, of course the hardware of the streamer and DAC. I suspect if they get Spotify into MU3, or into MU2 via firmware, you’ll find Spotify’s MUCH larger library will sound just as good. Tidal is now around 96% of the library (but UX still sucks) and Qobuz is for very limited tastes with 40% of Spotify’s global library. Stats from Spundiiz with my own playlists — around 120,000 songs of many genres.
I carefully read your review of the MU2. This week I went to a friend who had the MU 2 in his system. He is an experienced audiophile. It has a large hall built high up. He told me that he had never heard a dac sound so good. He uses the MU2 with his pre-amp. I also liked it.
I have the INNUOS STATEMENT, with the APL DSD-SR-SE dac. How would you compare these two DAC-STREAMERs? What are their characteristics in relation to each other? Do you have a preference? You have already published an article on APL’s DSD-AR.
Thank you so much
Tough to compare and extrapolate off the top of my head, and with a server that I have never heard in a controlled environment, let alone compared to other servers. I’d be inclined to think the two may be comparable in quality although there will undoubtedly be differences. These will be of personal preference. I recommend trying it for yourself.
Goedendag
Kunt u mij een advies geven over het volgende.
Ik speel nu met een soulution 711 via een sotm ultra streamer op een msb analog dac met (goede) analoge volume regeling module op magico Q3.
De bediening van de sotm via ipeng is erg complex. Ik heb derhalve een Roon licentie genomen en dit rechtstreeks aangesloten via de V2 renderer module opi de dac. Het geluid is sindsdien erg vlak/saai geworden waardoor ik op zoek ben naar een alternatief. Ik overweeg een mu2 van Grimm maar heb twijfels of het niet beter is om bv een aurender of mu 1 te combineren met de analog dac en t.z.t. een aparte voorversterker vb een soulution 725 of ch Precision te gebruiken. Deze laatste optie lijkt me muzikaal gezien de beste echter prijzig of zou een mu2 ook deze kwaliteit geven
Mvg Ruud Warringa
Hi Ruud, as you found, Roon has a different sound than MPD and UPnP, and depending on your system and preferences, one can be preferred over the other by a significant margin. To me, Roon sounds smooth, rich, and fluid, but it is not the last word in speed, articulation, transient sharpness, and expression. However, I would not refer to Roon as “flat” so maybe there’s another culprit or something that can be done to offset the change and restore the balance. If you like the SOtM, then another remote app might be a solution. You could try Rigelian, or search for other MPD-compatible apps. Aurender also works with MPD, and their app is an adaptation of the mpad app. Between MU1 + DAC versus MU2, the latter achieves a very high quality and is cost-effective, but the former offers more freedom to choose a DAC according to your desired voicing. The preamp section of the MU2 is very transparent but no true alternative for a CH L1 or Soulution 725.
Roon’s character is audible on every server, so, if you prefer UPnP, then I recommend finding another solution. Aurender works with MPD which is typically easy to operate, and has the potential to sound close to UPnP. However, the implementation has a large impact, and I would be hard-pressed to choose between an Aurender and the MU 1 or MU2.
Hi Christiaan,
Can you please tell me who made the acoustic pannels (two grey looking blocks) you have on the front all?
Thanks.
They are Sirrahs, made by R.T.F.S. See my review.
PS: each of my reviews has an Associated Equipment link at the bottom, as well as a link to the particular composition of the system at the time of the review.
Hi Christiaan
I’m currently debating over whether to buy the MU1 or MU2. Following your review, a few questions:
1. Is the MU2 in server/streamer mode perhaps a tad politer than the MU1?
2. If a user was after an existing, toe-tapping sound, which DAC would you recommend be paired with the MU1?
3. With regards Roon, I too share your assessment of it but hasn’t Grimm worked with Roon to mitigate the software’s somewhat softer, recessed sound signature?
Any feedback gratefully received.
And thanks for all your articles and insights. I often read your site.
Hi John, thanks for the feedback, nice to hear you like my work! Although it is hard to compare a server with built-in DAC to a server with an external DAC of choice, I would indeed say the MU2 leans to the polite side. It is suggested that Grimm “worked with Roon to mitigate the software’s somewhat softer, recessed sound signature”, but I don’t believe they have tuned the server in any way. They strive for a neutral-sounding and correct-measuring performance. Nevertheless, when I first reviewed the MU1, I had a hunch that the server’s balance of hardware and software compensated for Roon’s signature, as the MU1 was the liveliest Roon server I heard, bettering even my best UPnP endpoint at that time. A few updates later, however, the MU1 sounds more refined, airier, lusher, and indeed also relatively more polite. The MU2 is brilliant in providing superb resolution in a fluid and “analog” manner, but if you want the freedom to tune the sound to your liking, the MU1 may be a better choice. Two great DACs for the MU1 are the Aqua Formula xHD and Mola Mola Tambaqui. Other DAC brands that sound exciting and toe-tapping that spring to mind are Denafrips, Laiv, COS, and dCS. The best DACs I heard, price no object, are Playback Designs and CH Precision.
Thank you. While the MU1 provides some tuning flexibility (with a separate DAC), I may now look at alternative servers/streamers that don’t rely solely on Roon (despite the recent update that claimed to improve SQ). The LinQ is one. And thanks for the DAC recommendations. The Laiv is an interesting option: some reviews say it’s laid-back and warm, others say it’s exciting and energetic. Maybe it’s both.
Hi John, FWIW, I would describe the Laiv Harmony DAC as neither warm nor laidback. Ultimately, your own ears should be the judge:-)